Various vehicle collision determining systems have been proposed that can automatically detect the occurrence of a collision. These systems can function in combination with a passenger protection device, such as an inflatable airbag, such that the operation of the protection device depends on the occurrence of a collision. For instance, when the vehicle collision determining device detects the occurrence of a collision, a signal is transmitted to thereby cause inflation of an airbag.
In such a system, various sensors are used as collision detection sensors. For example, an acceleration sensor can be installed near a center pillar on a vehicle side to detect an acceleration change indicative of a side impact collision. In another example, a pressure sensor is installed in a vehicle door to detect pressure change therein and thereby detect a collision. U.S. Pat. No. 5,748,075 (Japanese Patent No. 2,654,428) discloses such a system.
FIG. 11 is a schematic illustration of a prior art vehicle passenger protection system with a collision determination system. As shown, the passenger protection system 101 includes a control circuit 110, a main sensor 160, a safing sensor 162, a drive circuit 180, and a vehicle passenger protection device 190. The control circuit 110 includes a determination circuit 120, an input/output (I/O) circuit 130, ROM 140, and RAM 150. The main sensor 160 is a collision detection sensor (e.g. acceleration sensor or pressure sensor) that detects the occurrence of a collision. The safing sensor 162 is a collision detection sensor that detects impact in the same direction as the main sensor 160 to thereby provide redundancy for added reliability of the determination circuit 120.
However, these prior art systems suffer from certain disadvantages. For instance, vehicles can include a relatively high number of collision sensors. Furthermore, more advanced microcomputers are used to handle the increased computing load necessary for communication with the increased number of sensors. This leads to increased costs.
Moreover, prior art systems typically detect the occurrence of a collision without regard to the behavior of the vehicle and instead rely solely on the output of the collision sensors. As such, a collision may be inaccurately detected in certain situations, such as when the vehicle door is opened and impacts a stationary obstacle.